Manufacture of artificial sponges



Patented Jan. 11, 1938 UNITED STATES A'E'ENT OFFICE 2,105,380 7 MANUFACTURE OF ARTIFICIAL SPONGES Joseph Speijer, Amsterdam, Netherlands No Drawing. Application January 18, 1936, Se-- rial No. 59,792. In Great Britain April 24, 1935 2 Claims. (Cl. 18-48) a It has heretofore been proposed to produce arway inner irregularities are prevented and that tificial sponges by mixing viscose with fibrous the product will be thereby maintained more materials and pore-forming substances and subhomogeneous. sequently coagulating the viscose. As a rule crystals of non-acid inorganic salts For this purpose several ways have been sugare to be used as pore-forming fillers. In ac- 5 gested using ripened or unripened viscose. In cordance with my invention it is desirable not to general the use of ripened viscose has the drawuse specifically coagulating salts or acid salts, as back that it yields a product of inferior quality has been suggested according to certain prior due to the low strength of the product. When patent specifications. Specifically coagulating using unripened viscose foam-forming substances salts are the salts of ammonia and of poly-valent 10 or anhydroussalts have been employed, which metals, and more especially the acid salts, i. e. latter may cause an undue coagulation when the salts with acid reaction such as NaHSOr or appliedfin relatively large quantities. NaHCO; or the like, because of the neutraliz- According to one suggestion a mixture is made ing action on the alkali in the viscose. Accordfrom ordinary unripened viscose, prepared from ing to the present invention salts are used which 15 unripened alkali cellulose by adding in addition to being without anysubstantial coagulating action on the viscose in the cold, will or Na'2SO4+H2O melt in their own water of crystallization when together with a proportion of anhydrous sodium subsequently heated. For this purpose, salts 2Q sulphate so that the mixture consists of which melt in their own water of crystallization when heated to about 100 C. (or at any event Na2s04+90 or 641-120, when heatedto not over 150 C.) are prefer- This mass is placed in a strong coagulating bath, ably used. I a hot solution of sodium sulphate being a Some examples of such salts are: 25 strong coagulator. 25

According to another suggestion ordinary vis- V ggfg t fi zgg cose is mixed with pore-forming fillers. The Nazsoy 10 aq 32 4 mass is heated under excess pressure in a regenerating bath. In order to avoid difiiculties acggggga g 3 cruing from the ripeness of the viscose an alka- Nazcoa i a'q line regenerating bath is employed. N32340:! 10 None of these proposals however pay any attention to the uneven coagulation which will oc- In regenerating the mixture one proceeds prefcur even if unripened viscose is used, because it erably in such a way that the outside of the always takes a long time (say 2-4 hours) before cake to be regenerated (in a mold, or not) 35 the mixing of the mass produces a satisfactory obtains a certain degree of solidity as soon as homogeneous product, and during this lapse of possible, e. g. by bringing the mass into a very time ordinary viscose will start to coagulate even warm environment. In this operation, the molds in the presence of sodium sulphate, although are preferably brought into a heated chamber 0 sodium sulphate is not a strong coagulator for (e. g. a chamber heated directly or indirectly by 40 ordinary unripened viscose when used at room steam, to about 100 C. or somewhat higher),

temperature. which heat may be continued for 3 to 15 hours, According to the present invention unripened 6 hours being suitable. Here heat may serve viscose is used as an initial material to which as the regenerating medium. The masses (in an extra quantity of carbon disulphide is added, molds or not) can then be placed into a heated 5 e. g. 10% of the quantity which has been used waterbath'in order to dissolve and remove the for the xanthation, the addition being made impore-forming substances. It is also possible to mediately before or during the mixing with fibres place the masses in a setting bath substantially and pore-forming materials. I will hereinafter consisting of a watery solution of sodium suluse the term extra CS2 to designate this carphide and sodium sulphate. This solution may 50 bon disulphide added after the xanthation treatserve as the regenerating bath, sodium sulphide ment, in which CS2 is employed, e. g. as usual. also acting as the desulphurizing agent.

In this way local coagulation is prevented dur- It is usually advisable not to subject the mixing the mixing operation, which latter always ture of viscose, etc., and salts, to a too high temtakes some time. It will be clear that in this perature because of the fact that temperatures 55 or centrifuging the mixture down to about 430 parts. This presscake (alkali cellulose) will contain about 100 parts of cellulose, about 60 parts of NaOH and about 270 parts of water: to parts of CS2 are allowed to act upon the comminuted alkali cellulose, in the usual manner, to

xanthate the same. The xanthated material isthen dissolved in such amounts of water and caustic soda as to give a viscose containing pref erably about 6-8% of cellulose, and about 5-7% of NaOH. Or the xanthate can be dissolved in water alone if desired. To the freshly prepared viscose is added (per 100 parts of cellulose contained therein) about 10-30 parts of fibres (e. g.,

:. flock of cotton, flax, hemp, etc.) and about 3-4 parts of CS2 (i. e. the extra CS2 mentioned above) This latter quantity of CS2 is preferably added While thoroughly mixing the fibres with the viscose. Then to the mixture of viscose, fibres and extra carbon bisulphide (i. e., the 3-4 parts added after the xanthation and dissolution have been carried out) is at once added one or several of the crystalline salts mentioned above, e. g., a quantity of 300-800 parts by weight for every 100 parts by weight of viscose.

If the crystals are small (e. g., passing a 20 mesh screen and retained on a mesh screen) this will produce small fine pores in the resulting sponge, while large crystals with an average diameter of to inch will produce larger pores in the sponge.

The mass obtained in this way is introduced into molds and thereupon the mass is subjected to a very warm atmosphere (for, say, 6 hours) or this can be done after a period (say 2-4 hours) of rest in order to allow the mass to become as homogeneous as possible. In consideration of the fact that the regeneration of the cellulose takes place quicker at a higher temperature, it will be evident that temperatures above C. are desired to shorten the reaction. The heating of the molds is then carried out as indicated above, and also the treatment with the setting bath.

After regeneration, the washing, desulphurization (if needed as a separate step), bleaching and such like operations can be carried out as I usual.

It will be evident to the expert that many modifications may be carried out lying within the scope of the present invention. For example, the proportions and the sequence of the additions may be varied within considerable limits, e. g;, the extra carbon disulphide may be added before the fibers are added, or it may be added simultaneously with the crystals.

I claim:--

l. A process of manufacturing artificial sponges from viscose which comprises adding extra carbon disulphide and pore-forming material solids to unripened viscose, the extra carbon disulphide being in addition to that used in the xanthation of the cellulose, said extra carbon disulphide being in amount capable of preventing premature coagulation of the viscose by the pore-forming solids, and'reg-enerating the cellulose of the viscose, while the pore-forming solid c remains chemically undecomposed.

2. In a process of making artificial sponge the steps of adding to unripened viscose, about 3% to 4% of carbon disulphide, based on the cellulose content of the said viscose, and adding an amount of crystals, containing water of crystallization, which is, substantially larger than the amount of cellulose, said crystals being such as can melt in their own Water of crystallization at temperatures not above C., and being crystals which do not exert a substantial coagulation action on viscose in the cold, making the mixture uniform and then subjecting the viscose to co-' agulation by heat, and heating the mass sufiiciently to cause the crystals to melt, and washing the spongeso produced.

JOSEPH SPEIJER. 

